The present invention relates to an improved fluid balance ring for rotating objects, such as a washing machine tub.
Fluid balance rings are well known for correcting unbalanced loads in rotating machines, such as the tub of a washing machine. Such fluid balance rings are effective at high rotational speeds to counterbalance unbalanced loads resulting from objects in the tub being unevenly distributed or off-center. An example of such a situation is a load of towels positioned along one side of the rotating washing machine tub, which create an unbalance. Such an unbalanced condition causes deflections in the rotating tub. The deflection of the unbalanced tub increases as the rotational speed of the tub increases, up to a critical speed, after which the deflections are minimized by the function of the fluid balance ring. The critical rotational speed varies from assembly to assembly, depending on the structure, mass, and geometry of the rotating assembly and its contents. The fluid within the balance ring counteracts the unbalanced load in the tub when the tub is rotating at high speeds.
One problem with prior art fluid balance rings is that the ring is only partially filled with fluid. Thus, the mass of the ring is insufficient to substantially reduce deflections of an unbalanced tub when the tub begins the spin cycle and is ramping up to its critical speed. Therefore the fluid balancing ring generally is not effective until the rotational speed of the tub reaches the critical speed.
Accordingly, a primary objective of the present invention is the provision of an improved fluid balance ring having sufficient mass to reduce tub deflections at low rotational speeds.
Another objective of the present invention is the provision of an improved method of balancing a rotating tub at low rotational speeds.
A further objective of the present invention is the provision of an improved fluid balance ring which is substantially filled with fluid at the beginning of the spin cycle, and approximately half full of fluid at the critical speed.
Another objective of the present invention is the provision of a fluid balance ring which is economical to manufacture, and durable and efficient in use.
These and other objectives will become apparent from the following description of the invention.
The fluid balance ring of the present invention is intended for use with rotating objects, such as a washing machine tub, so as to counterbalance unbalanced loads in the tub after the tub has reached its critical rotational speed, and to reduce tub deflections at rotational speeds below the critical speed. The balance ring is hollow so as to define a cavity therein. The ring is substantially filled with fluid, before the spin cycle begins, so as to provide sufficient mass to reduce deflections as the tub begins the spin cycle and ramps up through the critical speed. As the rotational velocity increases, approximately xc2xd of the fluid volume is drained from the ring. After the critical speed is reached, the remaining fluid is free to flow to a balancing position within the ring.